Air eddies occur on rotor blades of a rotary wing aircraft during operation. These eddies generate noise and vibration that are detectable, for example, in the cabin of the rotary wing aircraft and thus negatively affect the passengers' comfort. Such vibrations are additionally disadvantageous in terms of service life and maintenance, since they can result in material fatigue of the components and ongoing relative motion of the components, with wear associated therewith.
The causes of this noise and vibration are asymmetrical flow conditions and complex aeromechanical and aeroelastic phenomena, the collision of a rotor blade with blade eddies of a respectively leading rotor blade, and the forces that result therefrom and act on the rotor blade. In order to account to the greatest extent possible for different flight parameters and varying angles of attack, rotor blades in which the shape of the rotor blade in the trailing edge area can be changed are used. By specific adaptation of the rotor blade shape in the trailing edge area, noise and vibration can be reduced, and at the same time flight performance and flight trajectory can be improved.
Rotor blade flaps on the trailing edge of the rotor blade are known for this purpose in the existing art; these flaps are, for example, mounted movably on a rotor blade profile body with the aid of a pivoting bearing. DE 101 16 479 A1 describes one such rotor blade, the rotor blade flap being drivable via a piezoactuator that is arranged, spaced away from the flap in a profile depth direction, in a front profile region of the rotor blade profile body. The piezoactuator generates positioning forces, and transfers them to the rotor blade flap via ribbon- or bar-shaped tension elements.
With this type of rotor blade, the effectiveness of the rotor blade flap weakens after only a relatively short service life. DE 103 34 267 A1 therefore describes a rotor blade having an elastically movable rotor blade flap, such that piezoelectric actuators are mounted into the rigid covering skins of the blade profile, or immediately below the rigid covering skins, or on the rigid covering skins, so that one of the two piezoelectric actuators on the upper-side covering skin or lower-side covering skin of the blade profile can be selectably actuated, and thus causes a displacement of the respective covering skin relative to the other covering skin, which shortens or lengthens the upper covering skin relative to the lower covering skin. As a result of the relative shortening of one covering skin with respect to the other, the rigid rotor blade flap attached to the covering skins is deflected, and is moved upward or downward.
JP 8-216-997 describes a rotor blade for a helicopter in which the covering skin in the area surrounding the trailing edge of the rotor blade can expand and contract, at least in the direction of the profile chord, with the aid of a piezoelectric element.
A similar arrangement is also described in DE 103 04 530 A1, the piezoelectric actuators either being integrated into the profile, for which no flap is provided, or alternatively being provided exclusively in the flap. In the case of the piezoactuators provided in the flap, the profile flap is deformed by means of the piezoelectric actuators.